Abstract: In this study, to compare the numerical result of scour around a circular pier subjected to a steady current with experimental results an unstructured flexible mesh generated with rectangular flume dimension of 10 m wide, 1 m deep and 30 m long. The grain size of the sand was d = 0.16 mm, sediment size, sediment 50 gradation = 1.16, pier diameter D = 30 mm and depth averaged current velocity, U = 0.449 m/sec are considered in the model same as the flume experimental conditions. The two dimensional MIKE21 Flow Model (FM) and Sand Transport (ST) Module which is developed by Danish Hydraulic Institute (DHI), Denmark was used in the study. The estimated scour depth obtained from this model is validated with flume experimental results and it is observed that the results of the model have good agreement with flume experimental results. In order to compare the scour depth, several simulations were made change in sediment transport model description in the numerical model viz., Engelund-Hansen Model, Engelund-Fredsoe Model and Van Rijn Model for keeping constant pile diameter D = 0.03 m and for constant depth averaged current speed U = 0.449 m/sec. The results indicate that the scour depth estimates using Engelund-Hansen method gives high (factor 0.86) which is compares well the experimental results and Engelund-Fredsoe gives factor 0.32 and Van Rijn method gives low factor 0.23 when compared with flume experimental results. And also, it is observed that the scour depth S/D is the order of 1.73 for Engelund-Hansen Model, 0.64 for Engelund-Fredsoe Model and 0.46 for Van Rijn Model Hence, this MIKE21 FM-Sand Transport Model can be used as a suitable tool to estimate the scour depth for field applications. Moreover, to provide suitable scour protection methods, the maximum scour depth is to be predicted, Engelund-Hansen method can be adopted to estimate the scour depth in the steady current region.
P. Mohamed Rajab and K. Thiruvenkatasamy, 2018. Comparison of 2D-numerical Modelling of Local Scour Around a Circular Bridge Pier in Steady Current. Journal of Engineering and Applied Sciences, 13: 5243-5251.